The present invention relates to a chemical mechanical polishing aqueous dispersion, a method of preparing the same, a chemical mechanical polishing aqueous dispersion preparation kit, and a chemical mechanical polishing method.
In recent years, lines (interconnects) formed in semiconductor devices have been increasingly reduced in dimension (width) along with an increase in the degree of integration of semiconductor devices. Therefore, a method that planarizes a wiring layer by chemical mechanical polishing (hereinafter may be referred to as “CMP”) has been used. For example, JP-T-2002-518845 discloses a damascene process that deposits a conductor metal (e.g., aluminum, copper, or tungsten) by sputtering, plating, or the like in a minute groove or hole formed in an insulating film (e.g., silicon oxide) formed on a semiconductor substrate, and removes a metal film unnecessarily stacked around the groove or hole by CMP while allowing the metal to remain in the groove or hole.
In particular, tungsten that exhibits an excellent embedding capability is used for a via-hole that electrically connects lines in the vertical direction. For example, JP-T-2005-518091 discloses a polishing composition that contains an oxidizing agent (e.g., hydrogen peroxide), an iron catalyst (e.g., iron nitrate), and abrasive grains (e.g., silica) as a chemical mechanical polishing aqueous dispersion used to polish a tungsten film. A chemical mechanical polishing aqueous dispersion used to polish a tungsten film is required to exhibit a higher polishing rate and produce a flat polished surface. JP-A-2007-19093 and JP-T-2008-503875 disclose technology that adds a water-soluble polymer to a polishing composition in order to achieve the above properties in a well-balanced manner. However, a tungsten film-polishing aqueous dispersion that can achieve the above properties in a well-balanced manner has not been proposed.
A chemical mechanical polishing aqueous dispersion used to polish a tungsten film has a problem in that abrasive grains such as silica aggregate during long-term storage. A chemical mechanical polishing aqueous dispersion in which the abrasive grains aggregate cannot exhibit the desired polishing performance, so that various polishing defects may occur on the polishing target surface. For example, when a wiring layer is polished to a large extent, a depression referred to as dishing or erosion may occur. Surface defects referred to as scratches may also occur on the polishing target surface due to aggregated abrasive grains.
Since a chemical mechanical polishing aqueous dispersion used to polish a tungsten film tends to change in polishing performance during long-term storage, development of a means that can provide a chemical mechanical polishing aqueous dispersion having a constant quality has been desired. In particular, the above problems significantly occur when providing a chemical mechanical polishing aqueous dispersion in a concentrated state. Therefore, an improvement has been desired.